Ensure DeleteUser is not allowed to Delete Orgs and visa versa (#10134)

* add check to DeleteUser

* add check to DeleteOrganization

* add Test

* remove redundancy (deleteOrg is only used in DeleteOrganization)

* Update models/org.go

Co-authored-by: zeripath <art27@cantab.net>

models/user_test.go

@@ -199,6 +199,9 @@ func TestDeleteUser(t *testing.T) {
 	test(4)
 	test(8)
 	test(11)
+
+	org := AssertExistsAndLoadBean(t, &User{ID: 3}).(*User)
+	assert.Error(t, DeleteUser(org))
 }
 
 func TestEmailNotificationPreferences(t *testing.T) {